I left school at 15.
By the time I wanted to join the RAF for pilot training I was a 22yo marine engineer but did not have the 5 'O'-levels required at the time.
I asked the RAF whether, if I obtained the necessary qualifications, they'd interview me. They said : No promises - get them and reapply.
I asked the Principal of the technical college at which I'd studied as an apprentice if they would present me for the 'O'-level exams when they came around BUT without attending classes - I'd do all my study at night and weekends so that I could work (for IBM on quality control). I could hardly believe it when he agreed.
It all worked out.
As others have said, I wouldn't join in the ranks hoping to be selected; that just adds another level to get through. I'd counsel getting the qualifications; don't forget that, even if you don't make selection, they are still there for other applications.
Have you had a medical examination to check that your bits are OK for military flying? Eyesight can be a stopper.
Plus point: It was 1965. Thank you, John and Nikita, for failing to play nicely together
p.s. Re what others have said: Can you apply for AAC NCO pilot training selection directly as a civilian. Someone mentioned RA as useful trade training. What? Royal Artillery? OK, I've met some civilians the RA could usefully apply themselves to
Best of luck!